Correct a door handle that only opens when lifted -- rather than depressed -- by removing the screws that hold the casing in place.
Take off the exposed lever and set aside.
Insert the end of your pinkie finger into the exposed round washer, surrounded by a bevel.
Turn the washer 90 degrees with the tip of your finger to reset the mechanism.
Replace the same lever and the screws you previously removed. The door should now function properly.
Loosen all the screws in the doorknob.
Lift up on the exterior side of the knob.
Re-tighten every screw in the doorknob.
Gently allow the doorknob to be lowered down. This series of minor adjustments will keep the spindle from binding, and make it more level with the latch mechanism.